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Aquatic Exercise and Bone Density

Guest Blogger: S'WET™ Instructor Irene Pluim Mentz

We have always heard that to increase bone density, you need weight bearing activities, preferably with increased impact. But is that really so? With this article I hope to increase understanding of the mechanics needed to keep your bones strong and debunk the myth of needing high impact weight bearing exercise as the one and only option.

What is bone density exactly? The density of our bones is measured by the amount of minerals, mostly calcium and phosphorous, in a certain volume of bone. It means that if you have a higher amount of those minerals in your bones, your bones are stronger, more dense, than those of somebody with fewer of those minerals per volume unit of bone. And when something is more dense, it usually is stronger.

In this instance, it means you might be less likely to break a bone than somebody with a lower content of these minerals. And since bone fractures, especially in post menopausal women, is a major cause of disability, it would be beneficial to reduce that risk.

In many publications, it is recommended to walk, run, hike, dance, play tennis, or climb stairs to help maintain bone density. Recently strength training has been added to the list of activities that have a positive impact on the strength of our bones. But why are these things beneficial?

Let's dive into a bit of anatomy:

Muscles are attached to bone by tendons at the osteotendinous junction (OTJ). When muscles contract (shorten) the tendon pulls on the bone and makes it move. Every time there are forces transmitted from the OTJ to the bone, it elicits mineral absorption, increasing the amount of minerals per volume unit of bone i.e. increased density!

However, not all types of exercise deliver an equal amount of these osteogenic forces. To have a beneficial effect on the strength of the bone (bone density) the mechanical load needs to exceed that of your usual daily activities, hence the recommendation for hopping, jumping, and running. Progressive resistance exercises are included in this recommendation.

Resistance training, aka strength training, increases muscle strength. As your muscles grow stronger, they pull harder, more forcefully, on your bones, increase the mineral absorption, and therefore strengthening your bones.

Unfortunately the reverse is also true: a more sedentary lifestyle decreases muscle strength, which in turn diminishes the force applied on your bones. At that time, mineral absorption decreases, causing bones to become weaker. To continue the benefit of strength training, it will need to be progressive; meaning: if you do the same strength training routine over and over, it will become the new baseline and your body will adjust to that.

Most frequently, when we hear about osteoporosis we think of elderly women. And yes, it is true that women are at greater risk to lose some of their bone density. However, men are at risk too, especially if there is a history of having used steroids, anticonvulsants (seizure medication), cancer therapies and several other risk factors, including thyroid, kidney, or digestive system problems. About 50% of women over 50 years of age will fracture a bone due to osteoporosis where for men that statistic is about 1 in 4.

Aquatic fitness is a great modality for people who have been sedentary or already have some form of osteoporosis, since it cushions the impact on the joints, therefore minimizing possible pain or discomfort from joint related issues. However, due to the viscose nature of water, it provides a much greater resistance than typical land exercises do.

It also decreases the risk of falling, causing people to be more willing to try exercises that could potentially lead to loss of balance, such as single leg stands, hops, or even jumps. The variety of exercises, equipment choices, and depth level changes available in the pool give an unlimited amount of variety, aiding the need for continued progression to combat adaptation.

The AEA states the following: The resistance level of water just from physical movement places a demand on the skeletal system, thus placing a load on the bones. Once the bones are subjected to this stress they are forced to respond and increase muscle tension. This entire process results in stronger and denser bone, happening with just minimal movement.

Think what could happen is you added specific bone loading exercises and added resistance equipment yet to that (emphasis added by author).

Another finding has been that the impact on the bottom of the pool adds to the bone loading capacity. Even though this impact is reduced compared to land based exercises, it still provides the stress to the bones and therefore increases their strength. Not to say that deep water exercise does not have this value; rather, those participants have a greater water resistance factor to overcome and load their OTJ and thus their bones in that manner.

And on Oct 9, 2019, Playcore reported the following findings from research they found: While the control group demonstrated a decline in all measures, the aquatic exercise group increased bone mineral content while maintaining bone mineral density. The findings that aquatic exercise maintains bone density which prevents the expected yearly decline should (also) not be overlooked.


Do we need high impact exercise to maintain bone density? My conclusion is a resounding: NO. What we do need however, is a progressive overload of our OTJ and muscles to maintain the mineral content in our bones.

Can aquatic exercise be used to accomplish that: ABSOLUTELY!

Let's turn to our liquid gyms!


Irene Pluim Mentz, PT, ATRIC became a licensed physical therapist in the Netherlands before immigrating to the United States. She is the co-owner of One Step Beyond, Inc. Physical Therapy.

Irene’s passion for anything “water” led to becoming an AEA certified instructor. She integrates her knowledge of hydro-dynamics with physical therapy into all her sessions. Irene is the inventor and developer of the Aqua-Ω adjustable drag resistance water exercise equipment.

Find Irene Online:



Be sure to find Irene and the rest of our S'WET™ SQUAD demonstrating the incredible power of The Aqua-Ohm!

Turbulence Training with Irene Pluim Mentz featuring Aqua-Ohm

Friday August 4th (7:00 – 8:15am)

Let’s create some turbulence to spice up your water aerobics, boot camp, warm water, rehab, and personal training sessions. Explore how the Aqua-Ohm can add resistance to arms and legs and challenge the core. This equipment, part of the Liquid Gym Toolkit, effortlessly adjusts for size and resistance level.

The Power of Ω with Katy Coffey

Saturday, August 5th (7:00-8:15 am)

Gain deeper understanding on a multi-purpose tool for all levels. AquaFIIT strength training technique features the Aqua Ω as its key training tool. Alternating between cardio, strength, upper and lower body, this one powerful tool is sure to give you a full body drag workout. Learn how to effectively design and implement an aquatic resistance-training program that maximizes results while remaining on budget.

And check out all the other workshops we'll be offering in Reston, VA @ DCAC this year:


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